1. Field
The present disclosure relates to printed circuit board assembly techniques, and more particularly, to the attachment of temperature sensitive components designed for surface mounting.
2. Description of the Prior Art
By way of background, many electronic components have a manufacturer-specified thermal processing limit that is not allowed to be exceeded during printed circuit board assembly. Violation of a component's thermal processing limit will degrade the reliability of the component and may void the manufacturer's warranty. Some surface mount assembly techniques require temperatures that are incompatible with certain classes of temperature sensitive components (TSCs). For example, the assembly of lead-free circuit boards will typically require a high temperature lead-free solder reflow process in an oven. TSCs that may be incompatible with such processing include polymer or aluminum capacitors.
One known technique for avoiding TSC overheating during high temperature reflow processing is to solder the TSCs to the circuit board with a soldering iron following the reflow operation. Another known technique is to perform a second solder reflow process that attaches TSCs using a lower melting lead-free alloy. A further known technique is to attach the TSCs to the circuit board using conductive adhesive at room temperature. A still further known technique is to shield the TSCs in the reflow oven to prevent overheating. Yet another known technique is to solder or otherwise attach the TSCs to a plated through hole (PTH) daughter card that is attached to the main circuit board.
Although the foregoing known techniques are all practical solutions that have been used in the past and currently to solve the TSC overheating problem, such solutions have various disadvantages. These include, but are not limited to, requirements for tight control of the heating source, unique circuit board designs or configuration changes to accommodate the processing, unique heat shield designs, qualification of low-melt lead-free alloy, and constraints on the rework capabilities of conductive adhesive. It is to improvements in the field of surface mount component attachment that the present disclosure is directed.